Metallic-vapor discharge device



Patented Nov. 17, 1942 METALL IC-VAPOR DISCHARGE DEVICE Max Steenbeck,Berlin-Siemensstadt, Germany; vestcd in the Alien Property CustodianApplication August 20, 1940, Serial No.`35 3,33 6 In Germany July 6,1939 V 7 Claims. (Cl. 250-275) This invention relates to gaseouselectrical discharge devices, particularly for operation at highvoltages. It is known to provide the discharge vessel oi' such deviceswith inserts which are arranged in the discharge path and impressed witha voltage lying between the anode and cathode voltages. The insertsconsist of annular members which create an electric field between everytwo adjacent inserts such as substantialiy occurs between concentricspherical shells.

The inserts in such a metallic-vapor discharge device reduce back firesto a `considerable extent, since the ions are deflected in thenon-conducting period towards particular re-combnation surfaces by theelectric field produced by the inserts,

so that a fresh formation of ions due to impact.

ionization is substantially avoided. However, the known arrangementsoften present the drawback that the inserts incur a considerableincrease of the arc drop voltage. It is true that in discharge devicesoperated at high vcltages the losses caused by the increase of the aredrop voltage are not appreciable as regards the emciency of the device.However, these losses cause a considerable development of heat which isdificult to dissipate in discharge devices for high current intensities.

The object of the present invention is to provide a discharge devicewith annular inserts between the anode and cathode, in which only asmall arc drop voltage is required, while retaining the protectionagainst back fires. This is accomplished, according to the invention byproviding composite annular members whose inner portions have theirsurfaces inclined with respect to the discharge path to a greater degreethan the outer portions. In this manner an increased number of ionsimpinge-upon the surfaces of the annular members during thenon-conducting period. By the use of such inserts a considerablede-iom'zation of the ions is attained in the nonconducting period, inwhich the ions follow the radially directed field, whereas in theconductng period the ions may reach the electrodes Without hindrance,since the control efiect of the' inserts is rendered ineifective by theplasma of the discharge. The central member is designed preferably inthe shape of a bowl so as to also prevent the ions from fiowing alongthe central axis.

Further details will be apparent from the description of an embodimentof the' invention illustrated in the accompanying drawing in which Fig.1 shows diagrammatically a longitudinal section through a dischargetube, Fig. 2 part of another embodiment, and Fig. 3 a portion of therectifier tube of Fig. 2 on a larger scale.

Referring to Fig. 1, l is the discharge vessel, for instance of ceramicmaterial, [0 a mercury cathode from which an auxiliary arc passes to anauxiliary anode ll, |2 is the main' anode, l'l an alternating currentsource, and |8 a currentconsuming apparatus to be fed from sourcellthrough the rectifying discharge device. Two control grids l3 and !4 arearranged within a metallic shield !9 and connected with a direct currentsource IE supplyingta positive bias to grid a, and with a control set l5supplying grid M with an alternating grid voltage. As iaras describedabove, the arrangement issimlar to the one more fully disclosed in myPatent No. 2,205,230, and merely incidental to the present inventionproper. According to the 'present invention, the tube shown in Fig. 1 isprovided with a set of composite inserts 2 which will be described inthe following with reference to Fig. 3. Fig. 2 shows a similararrangement except that the inserts 2 are arranged in an invertedposition.

As apparent from Fig. 3, each of the inserts is composed of annularmembers 3, 4, 5 and 6 and of a bowl-shaped central member 1. Theindividual members forming an insert are secured together by means ofinsulatng bridgng members. During the non-conducting period an electricfield is produced between two adjacent inserts substantially asoccurring between two concentric spherical shells. The lines of force ofeach field run substantially as indicated by the dash lines 8. Thesurfaces of the individual members.

forming the inserts are somewhat inclined to the axis of the vessel sothat in the non-conducting period the greatest possible number of ionsfollowingthe electric field of the inserts are intercepted by thesurfaces of the inserts, whereas in the conducting period this controlaction of the inserts is rendered ineffective by the predominant effectof the main discharge between the main anode and cathode.

The annular members 4, 5 and 6 have preferably 'such a height that the`lines of force 8 coming from the center of the spherical field cannotfreely pass through an insert. The intercepting surfaces of the insertoverlap one another to a slight extent as regards these radial lines offorce. It is also possible to prevent an undue amount of heat from beingdeveloped in the central portions of the inserts. To this end, it isonly necessary to make the passages between the inner members of eachinsert member longer than the passages'ofiered to the 'discharge betweenthe' outer members of each composite insert. As a result, the dischargecurrent, when passing through an insert, is throttled near the innermembers as compared with the portion of the discharge current passingbetween the outer tral portions is not unduly prevented. Particularattention must further be directed to the design of the outer members 3of the inserts, to prevent the formation of discharges between the parts3 and the wall l of the vessel. To this end, the member 3 extends ratherclosely to the wall I and is considerably longer in the direction of thedischarge path than the other insert members. In the discharge deviceshown in Fig. l, the sheld !9 forms part of the outer member 3 of one ofthe inserts 2.

Since the inserts are non-symmetrically designed With respect toopposite discharge directions, they may, to a certain degree, effect avalve action. For this reason the inserts are positioned in rectifierswith respect to the cathode and anode preferably in a difierert mannerthan in inverted -converter, i. e. the inserts are preferably invertedas exemplied by Figs. 1 and 2.

What is claimed is:

1. A uniaterally-conducting gaseous electrical discharge device having a:cathode and an anode forming the electrodes of a discharge path, andconductive inserts arranged coaxial and transverse to said dischargepath to assume voltages between the cathode and anode voltages, saidinserts consisting each of a composite structure comprising a pluralityof concentric annular members spaced radially from one another, each ofsaid members having a surface inclined With respect to said dischargepath, the inclination of the surfaces of the inner members of the insertstructure being greater than the inclination of the surfaces of theouter members of the insert structure.

2. A unilaterally-conducting gaseous electrcal discharge device having acathode and an anode forming the electrodes of a discharge path, andconductive inserts arranged coaxial and trans- Verse to said dischargepath to assume voltages between the cathode and anode voltages, saidinserts consisting each of a composite structure composed of a pluralityof concentric annular members spaced radially from each other andarranged so that the insert structure has in general a curved shapefollowing the general curvature of the adjacent insert structure so asto produce an electric field substantially such as occurrng betweenconcentric spherical shells, each of said members having a surfaceinclined towards said discharge path, the inclination of the surfaces ofthe inner members of the insert structure being greater than theinclination of the surfaces of the outer members of the insertstructure.

3. A unilaterally-conducting gaseous electrical discharge device havinga cathode and an anode orming the electrodes of a discharge path, and

conductive inserts arranged coaxial and trans-' verse to said dischargepath to assume voltages between the cathode and anode voltages, saidinserts consisting of a composite structure composed of a centralcup-shaped member and annular members concentrically surrounding saidcentral member, said members having surfaces inclined towards the axisof the structure, the inclination of the surfaces of the inner membersof the insert structure being greater than the inclination of thesurfaces of the outer members of the insert structure.

4. A unilaterally-conducting gaseous electrical discharge device havinga cathode and an anode forming the electrodes of a discharge path, andconductive inserts arranged coaxial and tranuverse to said dischargepath to assume voltages between the cathode and anode voltages, saidinserts consisting each of a composite structure comprising a pluralityof concentric annular members spaced radially from one another andhaving inclined surfaces as regards the axis of the discharge path, theinclination of the surfaces of the inner members of the insert structurebeing greater than the inclination of the 'surfaces of the outer membersof the insert structure, said members'of each insert structure beingarranged in staggered relationship and overlapping one another so thatthe substantially radal lines of force of the electric field establishedbetween adjacent insert structures during the non-conductive period andextending from one insert structure towards the adjacent insertstructure are preverted from extending through the anrular gaps betweenthe members of said adjacent structure.

5. A unilaterally conducting gaseous electrical discharge device havinga cathode and an anode forming the electrodes of a discharge path, and'conductive inserts arranged coaxial and transverse to said dischargepath to assume voltages between the cathode and anode voltages, saidin-- serts consisting each of a composite structure comprising aplurality of concentric annular members spaced radially from one anotherand having inclined surfaces as regards the axis of the discharge path,the inclination of the surfaces of the inner members of the insertstructure being greater than the inclination of the surfaces of theouter members of the insert structure, said members of each insertstructure being arranged in staggered relationship and overlapping oneanother in a degree increasing from the outer towards the inner membersof the structure 'so that the interstitial annular passages for thedischarge are longer between inner insert members than between outerinsert members.

6. A unilaterally-conducting gaseous electrical discharge device havinga cathode and an anode forming the electrodes of a discharge path, andconductive inserts arranged coaxial and transverse to said dischargepath to assume voltages between the cathode and anode voltages, saidinserts consisting each of a composite structure comprising a pluralityof concentric annular members spaced radially from one another andhaving inclined surfaces as regards the axis of the discharge path, theinclination of the surfaces of the inner members of the insert structurebeing greater than the inclination of the surfaces of the outer membersof the insert structure, said members of each insert structure beingarranged in stepped relationship, each inner insert projecting from theadjacent outer insert to permit heat dissipation by radiation from theinner inserts.

7. A unilaterally-conducting gaseous electrical discharge device havinga cathode and an anode forming the electrodes of a discharge path, andconductive inserts arranged coaxial and trans- Verse to said dischargepath to assume voltages between the cathode and anode voltages, saidinserts consisting each of a composite structure comprising a, pluralityof concentric annuiar members spaced radally from one another and havingsurfaces inclined towards the axs of the discharge path, said members ofeach insert structure overlapping one another so that the lines of forceof the electric field established between adjacent insert structuresduring the nonconductive period and extending from one insert structuretoward-is the adjacent insert structure are prevented from extendingthrough the annular gaps between the members of said adiacent structure,the extent of the overlapping of said members increasing from the cutertowards the inner members of the structure so that the interstitialannular passages for the discharge are longer between inner insertmembers than between outer insert members.

MAX STEENBECK.

